﻿using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;

namespace BaseData.Common
{
    /// <summary>
    /// DES加密算法类
    /// </summary>
    public class DESEncrypt
    {
        /// <summary>
        /// 加密字符串
        /// </summary>
        /// <param name="oraString">要加密的字符串</param>
        /// <param name="key">加密密钥</param>
        /// <returns>加密后的字符串</returns>
        public static string Encrypt(string oraString, string key)
        {
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            //把字符串放到byte数组中  
            byte[] inputByteArray = Encoding.Default.GetBytes(oraString);

            //建立加密对象的密钥和偏移量  
            des.Key = ASCIIEncoding.ASCII.GetBytes(key);
            des.IV = ASCIIEncoding.ASCII.GetBytes(key);

            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();

            StringBuilder ret = new StringBuilder();
            foreach (byte b in ms.ToArray())
            {
                ret.AppendFormat("{0:X2}", b);
            }
            return ret.ToString();
        }

        /// <summary>
        /// 解密字符串
        /// </summary>
        /// <param name="encryptString">待解密字符串</param>
        /// <param name="key">解密密钥</param>
        /// <returns>解密后的字符串</returns>
        public static string Decrypt(string encryptString, string key)
        {
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            //Put the input string into the byte array  
            byte[] inputByteArray = new byte[encryptString.Length / 2];
            for (int x = 0; x < encryptString.Length / 2; x++)
            {
                int i = (Convert.ToInt32(encryptString.Substring(x * 2, 2), 16));
                inputByteArray[x] = (byte)i;
            }

            //建立加密对象的密钥和偏移量，此值重要，不能修改  
            des.Key = ASCIIEncoding.ASCII.GetBytes(key);
            des.IV = ASCIIEncoding.ASCII.GetBytes(key);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);
            //Flush the data through the crypto stream into the memory stream  
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            //Get the decrypted data back from the memory stream  
            //建立StringBuild对象，CreateDecrypt使用的是流对象，必须把解密后的文本变成流对象  
            StringBuilder ret = new StringBuilder();

            return System.Text.Encoding.Default.GetString(ms.ToArray());
        }
    }
}
